Q1: A ball is thrown from the location (x₀, y₀) = (0,0) of a horizontal playground with an initial speed v₀ at an angle θ₀ from the +x-direction. The ball is to be hit by a stone, which is thrown at the same time from the location (x₁, y₁) = (L,0). The stone is thrown at an angle (180° - θ₁) from the +x-direction with a suitable initial speed. For a fixed v₀, when (θ₀, θ₁) = (45°, 45°), the stone hits the ball after time T₁, and when (θ₀, θ₁) = (60°, 30°), it hits the ball after time T₂. In such a case, (T₁/T₂)² is _____. [JEE Advanced 2024 Paper 2]
Ans: 2
For Case I :
For Case II :
Also dx2/dt = speed of tip of person's shadow
Applying similar triangle rule in ΔABE and ΔDCE
Differentiate both sides w.r.t.
= 100 cm/s
This is the speed of the tip of the person's shadow with respect to the lamp post. But, we need to find the speed of the shadow's tip with respect to the person, which is the relative speed :
= 40 cms-1
So, horizontal displacement done by the projectile in new region is
So, n = 0.95d
Q1: Starting at time t = 0 from the origin with speed 1 ms-1, a particle follows a two-dimensional trajectory in the x-y plane so that its coordinates are related by the equation y = x2 / 2. The x and y components of its acceleration are denoted by ax and ay, respectively. Then [JEE Advanced 2020 Paper 2]
(a) ax = 1 ms-2 implies that when the particle is at the origin, ay = 1 ms-2
(b) ax = 0 implies ay = 1 ms-2 at all times
(c) at t = 0, the particle's velocity points in the x-direction
(d) ax = 0 implies that at t = 1s, the angle between the particle's velocity and the x axis is 45o
Ans: (b), (c) & (d)
Given, equation
y = x2 / 2
For option A :
when particle is at origin then x = 0.
Given that at origin, vx = 1 m/s
So, ay= (1)2 = 1 ms-2
At origin, 0 × ax = 0 means ay does not depend on the value of ax.
For option B :
When ax = 0 ⇒ vx = constant
So vx will stay 1 ms-1.
when ax = 0,
= 1 ms-2
For option C :
Velocity is always tangential to the path of motion of the particle. So at origin path is along x axis as tangent at origin along x axis.
For option D :
When ax = 0 ⇒ vx = constant
So vx will stay 1 ms-1.
At t = 1, x = 1 m
∴vy = xvx = 1 × 1 = 1
Now, slope of velocity at t = 1 is,
tanθ = vy / vx = 11 = 1
⇒ θ = 45o
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JEE Advanced Previous Year Questions (2018 - 2024): Motion
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Ans: 4.0
For first projectile,
For journey,
⇒ α = 4
If speed is v after the first collision, then speed should remain 1/√2 times, because kinetic energy has reduced to half.
⇒ hmax = 30 m
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